I recently upgraded my computers to Windows 8. I have QB Pro 2012 installed and shared between two computers. Since the upgrade I can't access the file on the main computer.
When I try to open it, I get "Cannot communicate with company file".
If I run the QB Connection Diagnostic tool while the file is open on the other PC, I get "File is in use".
If the file is closed on the other computer, sometimes it will open on my 2nd computer - and then we can open it on the first computer - and use from both places, but within a short time, QB freezes up.
I called support - they said QB 2012 isn't supported on Windows 8 (although their website does say it's compatible). And that unless I pay to upgrade to QB 2013 - I have to pay for support.
*sigh*

I run QB on a Mac using a virtual machine which runs Windows 7. I tried Windows 8 which was a nightmare. I would suggest using Windows 7, but not the Home Version, use Professional. With the understanding you do not or may not want to reinstall your operating system; you can create a virtual computer which runs in your current OS and install QB there. It will connect to other computers in a NETWORK DOMAIN as as well as a group network like "Home".

Go to the Microsoft Knowledge base and look up Virtual Computer, I believe it is still a free download. Windows 8 just isnt cutting it for the business environment. NOT A FAN. Good Luck